The 2015 river monitoring season gets underway

A guest blog post by Laura


This week marks the start of the ‘spring’ ecology sampling season for my team.  Today I was out collecting invertebrates in Upton, Pershore, Evesham and Broadway, in Worcestershire. I catch the creatures using a method called kick sampling. 

In a nutshell I kick around in the substrate and search under stones to look for invertebrates, they are collected in the net then transferred to a tray.

I pick out all the leaves, sticks and stones, checking none contain invertebrates.  The sample is then tipped back through the net, the water drained off and placed in the container.  

Data is then collected on substrate type, surrounding vegetation, width, depth, plant growth etc.  All this has an impact on the site and can affect the biological water quality and hence the type of creatures present.  Data is automatically uploaded onto a database. 

Once back at the lab the sample is preserved in methylated spirit so the it doesn’t degrade.

Each invertebrate has a score; 1 reflects poor (low) water quality and 10 is excellent (high) water quality.   The photo below shows leeches, molluscs and shrimp (I won’t bore you with the Latin names) from Mere Brook. This initially tells me the water quality is average as these species can tolerate heavy sedimentation and low water quality.  

However, the picture below shows a high scoring cased caddis crawling along the container, its case is made from tiny sand grains.

Cased caddis out of its case

Its’ presence shows the watercourse must be good quality.  Just from poking through the sample in the tray I can see lots of species that indicate good water quality.  Once under the microscope our experts can pick out the smaller species, the scores are added up and this gives the site an overall score for biological quality.


In the photo below can you spot the difference between the 2 inverts and the sticks? That is what samplers are trained to do.  You need attention to detail in this job!

In Piddle Brook at Pinvin and Seaford there were more high scoring inverts present, mostly different types of cased caddis fly larvae.  In photo below you can see the cased caddis fly larvae has crawled out of its case which is made from sand grains.  Some make a case out of tiny sticks and leaves.

The caddis fly larvae places 2 stones on either side of their case when constructing it that create ballast so it can crawl along the riverbed.  It is able to retreat into its case to prevent fish from eating it.  If it didn’t have ballast it would get swept away into the water column. 


I finished the day in Broadway kick sampling the Badsey Brook. Once back at the office, all 3 pairs of waders, trays, nets and gloves were disinfected and hung up to dry.  

This is what we call biosecurity. We take is very seriously as it can prevent the accidental transfer of diseases and invasive species from one waterbody to another.

They’ll be used in the Sud Brook at Gloucester tomorrow when the monitoring programme continues!


Fishy health checks in Shropshire

Our fish monitoring programme is now in full swing and our people have been undertaking lots of electric fishing surveys. On Wednesday 18th June we surveyed the River Onny near Onibury in Shropshire.

Using electric current we surveyed 100m of the River Onny and caught:

127 juvenile Salmon

18 Brown Trout

3 Grayling

2 large eels

We measured all the fish and removed 3 scales from each salmon and trout in order for them to aged by our Brampton Laboratory.

This is a fantastic result! We counted salmon redds (nests) on this same stretch in October and November last year and saw salmon spawning, redds and dead kelts (fish that have died from exhaustion after spawning).

The large numbers we caught shows the river in a great health and that not all the redds got washed away by the winter floods.

Staff from the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) joined us and took 30 salmon parr away to check if they have a parasite, Gyrodactylus salaris.

It is a category one notifiable disease. The parasite has decimated rivers in Norway and CEFAS check each catchment in the UK every 5 years. Luckily no parasites have been found in our rivers to date.

Catching fish in a half mile wide river

On 8-9th May we carried out the bi-annual fish sampling on the Severn Estuary at Arlingham. This is no simple task as not only is the river very wide, it’s also tidal, rising and falling many metres twice a day.

We use fyke nets. These are like a long narrowing tube with the wide end pointing upstream. Fish swim into the net and can’t escape. They have special attachments in the mouth to prevent otters entering and getting trapped.

The fyke nets are set at low tide in the estuary channel. After 24 hours the nets are checked and any fish species present are identified, counted, measured and released.

The dominant species caught were Mullet, Eel and Sea Bass.

The netting forms part of our WFD (Water Framework Directive) TRAC (Transitional and Coastal) monitoring programme. The data collected allows us to monitor the fish populations of the Severn estuary.


Little boats with a serious job to do

Among our many roles, we are responsible for the collection of information about the water cycle. We gather a variety of river level/flow data, weather and climate information and groundwater data.

Across Midlands region we have almost 500 measurement sites along our rivers. These range from our primary sites where a telemetry system automatically takes 96 readings each day, to logger sites where data may be manually downloaded once a month.

Much of this river level information is available online via the environment agency website here:

As well as measuring levels of water in rivers, we also need to measure flow. We can do this by using either a structure such as a weir or flume, or by putting equipment in the river. The results we get always have to be calibrated (checked) and this is where our lovely mobile boats and acoustic measurements are used.

The level and flow data we get is of vital importance as it is used to make key decisions in areas such as flood warning and forecasting, water resource management & abstraction and discharge management.

Our telemetry data also provides the triggers for flood warnings to be issued as well as the building blocks for our flood models which trigger flood defence deployment and the advice we give to our partners during times of flooding and drought.

We measure flow using sounds waves and the Doppler effect. This is the change in frequency of a sound wave for an observer moving relative to its source (so I’m told!).

Sensitive sensors are mounted on the underside of small boats and manoeuvred across the river. This is done either with ropes, cableways (bit boring) or more recently using our remote controlled boat (great fun).

As the sensor moves across the water surface, it fires high frequency sound waves to the bed of the river. These waves are then bounced back from the bed of the river and the return waves are altered by the Doppler effect of the flowing water. We measure this shift to give an accurate measurement of water speed or velocity.

The sound beam also measures the river depth and a GPS and built-in compass measures the width.

We then use basic maths to calculate flow – Q (flow) = V (water speed) x A (Area) (Width x depth)

As well as telling us the flow of the river, our boats also give a screenshot of the river channel shape. This is useful to establish if there are any underwater blockages within the channel that need removing or whether future erosion is going to affect the site.

Our little Q boats have been doing brisk business over the last few weeks’ flooding, helping to ensure our flood information and advice is as accurate as it can be.

Spawning salmon spotting in Shropshire

The River Onny is an important river for migratory Salmon, with numerous fish running the river to get to suitable spawning ground in the upper reaches.


To spawn salmon cut redds, which are shallow excavations in gravel beds, and lay their eggs at the tail end of the redds where the fertilised eggs can grow into alevins in the relative sanctuary of the deep gravel beds.


The simplest way to determine the amount of salmon that have run the river to spawn is to count the amount of redds that are cut over a set area and time period. This gives us a good idea of how strong the salmon run has been in any one year and therefore how this will relate to year class strength within the existing population.


On the stretch of the River Onny, from Stokesay to Onibury, that we surveyed last week 10 salmon redds were seen as well as a pair of salmon guarding a recently cut redd. Four dead cock fish and one dead hen fish were seen. This is all part of the natural life cycle as not all salmon make it back downstream due to exhaustion.